Shu was what Sichuan was called in ancient times. It is surrounded by mountains and it was notorious for its lack of accessibility. That became widely known partly due to a line from one of the most eminent Chinese poets, Li Bai (701-762). He lamented: "Traveling on the Shu Path is as difficult as ascending to heaven."
In those days all roads leading from the outside to Sichuan were referred to as the Shu Path, including those from Shaanxi and Gansu.
The most famous section of the Shu Path is about 600 kilometers long. It starts at Chengdu then passes Deyang and Guangyuan in Sichuan before ending in Hanzhong in Shaanxi. Construction of the section started around 316 BC. It was built on mountains so precipitous that the awe-struck Li Bai was inspired to mention it.
A plank road is on the cliff above the famous Valley of Love of the Luoshui River. The valley is so named because of a story in which its two characters do not live happily after.